Intermittent misfire

I can’t figure out this intermittent misfire my 98 2.4 Tacoma. In the dark I could see a little bit of spark leakage around the wires so I replaced the aftermarket plug wires with OEMs. Spark plugs were also replaced at this time. It seemed it might’ve been better but as the component heated up I’m again getting an intermittent misfire. The codes almost always show a misfire in cylinder 1, sometimes multiple cylinder misfire and a few occasions I’ve seen cylinder2 misfire code. It seems when it was running poorly quite often pulling the number 1 spark plug wire has little or no effect on the idle why the other 3 cylinders have much more effect. I replaced the 1 and 4 ignition coil pack and again it seemed like it was fixed but now its back. I’m thinking I will try the crankshaft position sensor next. Does this make sense? It has never thrown a P0335 code (crankshaft position sensor).

 

Dear KZK444,

How it going? Sorry to hear about your misfire dilemma. Unfortunately, I know Toyota's 5VZ-FE 3.4 V6 engine much better than I know either the 2.7 or 2.4 liter Toyota four cylinder engines. Please tell us how many miles you have on your 2.4 liter engine.

Okay, so let me try to help you out here. I have read in your post that you have replaced the obvious culprits of the problem being the spark plug wires or the spark plugs, and this exercise proved futile. What leads you to believe that the crankshaft position sensor is the problem? The crankshaft position sensor would have more to do with the truck not starting. If you replace the crankshaft position sensor, the only thing you are going to do to your Tacoma is remedy the Tacoma from throwing the P0335 Code. I don't think this is going to solve an intermittent firing problem, but I could be wrong.

While you were changing out the spark plugs and the spark plug wires, did you clean up the throttle body and the Idle Air Control? I see your firing sequence is controlled through ignition coil packs. You have definitely done your homework by replacing number one and four. Why did you not replace all of them while you were there? How long after you replaced your number 1 and 4 ignition coil packs before the intermittent firing dilemma came back? One thing to remember whenever working with ignition coil packs is to stress them very little. In fact, touch them whenever handling them as delicately as humanely possible. You probably already know this.

I hope my insight sheds some light on the problem.

Good Luck,
Paul

 

Might want to have your compression checked bud. If that tests out okay, you may want to consider getting your cylinder leakage integrity checked. This will rule out major engine troubles and then at which point if all checks out well that will point out fuel injector troubles.

If I remember correctly, 2.4 4 banger Toyota truck engines of that generation were notorious for valve issues. This is why I suggest checking out both of those major items to rule that entirely out first before chasing your tail any further.

 

Before you spend any more money on all these small electrical pieces that it could be, just cut straight to it and get two tests: Compression test and Leak down test. This will determine if you have an issue with your cylinder head/any valves.

I had a persistent cylinder 2 misfire in my 1996 2.7L and went on and on replacing plugs, wires, distributor cap and rotor, fuel injectors, etc. Then finally got a leak down test and determined I had compression escaping through the tail pipe, which was an indicator that I had a burnt exhaust valve, which I ultimately did. Replaced the cylinder head on my truck and the things been running perfectly ever since. Sucks if there is a burnt valve or a cracked head, but take it from me, it's not the end of the world.

 

Dear Roberto,

KZK444 said the problem was intermittent. Don't you think if it was a major engine problem, the problem would be more consistent.

Take it easy,
Paul

 

No, a burnt valve can cause intermittent misfires. It depends on how bad the valve is. It could run like that for months, and can get worse and worse as you lose more and more compression in the cylinder.

 

If you don't know how to perform these tests yourself or don't wish to than a mechanic can do them very quickly for you. But they usually cost about $100. One very cheap solution could be buying Mass Air Flow Sensor cleaner and cleaning you MAF sensor. Also, like Junkie said, you could try cleaning your throttle body. A quick google search will show you how to do both of these things. They are very easy little maintenance projects.

 

Austin,

The original poster said the problem went away for a while after he replaced the number 1 and number four ignition coil packs. Don't you think that if the problem was a burnt valve, the only way for the problem to go away is by doing head work.

Take it easy,
Paul

 

With a burnt valve the compression can be right on the borderline of allowing ignition of the fuel. A new coil and wires could give a slightly stronger spark thus allowing the fuel to ignite. Over time a burnt valve will only get worse as hot exhaust gas is constantly eroding the valve at the spot it's burnt, so over time if the misfire when away it will eventually come back.

Having said that it's possible it's just a bad injector or some other problem. The leakdown test can rule out a burnt valve and save a lot of time testing and replacing other parts if there is a burnt valve. It's great if you have the tools to do a leakdown test otherwise you'd have to pay for a mechanic to do it, so I can see understand why you might want to check/test other things first.

 

Wow!! I posted this Wednesday morning and Wednesday after work had no responses. A wake up this morning and 7 or 8 people have jumped on board here. Thank you so much for the responses. The engine has 310,000 miles on it. I didn’t do it leak down yet but the compression is good and the engine uses maybe one quarter of a quart between 10,000 mile synthetic oil changes. I have not cleaned the throttle body or idle air control yet. After changing the 1 and 4 coil the problem was back after about 20 minutes of driving. To clarify the problem comes and goes. I can be cruising with it missing and suddenly it stops missing and of course the truck just takes off. I’m thinking electrical because going to work in the morning when everything has had the whole night to cool off it runs good for 15 to 20 minutes before I get this intermittent problem. Going home when it’s warmer it seems like the problem starts sooner. Years ago I remember coming home from Vegas to Los Angeles in an 82 Toyota truck (20R motor) and the truck would just die. After sitting for 20 minutes I could drive for another 5. I wrapped the igniter with ice and wet rags and I could then drive for about an hour and when the ice melted and the rags dried out the truck would die again. I’m in the motorcycle business and it seems automobiles are somewhat different. A motorcycle has a pulser that lets the computer know where the crank is. Sometimes there are 2 pulsers, one for the 1 and 4 coil and one for the 2 and 3 coil. In these cases if a misfire is coming from a particular cylinder it would likely be one of these pulser’s and not the computer It seems like my problem is maybe a multi-cylinder misfire but I’m also suspecting that it could be cylinder 1. That is why I tried changing the one in 4 coil and did not do that 2 and 3. So…. It seems if the crank position sensor is breaking down the problem wouldn’t be just for cylinder 1 and less there is some going on the computer that I can’t understand. With these clarifications should I be looking at some of these other recommendations such as Mass Air Flow Sensor, throttle body, fuel injectors and idle air control? I just remembered something… About 40,000 miles ago I replaced a fuel injector with a non-OEM injector and I believe it was cylinder number 1. Next time the truck acts-up I’m going to pull over and put a large screwdriver on the number 1 injector and put my ear up to the handle and see if maybe there’s a problem here. (An effective trick I learned reading this informative forum)

 

I was going to suggest checking the injectors. Maybe try swapping them around to see if the misfire changes. Why did you replace the injector previously? Did you have a similar misfire? And when you replaced it did you use new o-rings and grommets so there's no leak?

Seems like a bad IAC or MAF wouldn't cause a misfire on a single cylinder.

With 300k+ miles it would be good to check valve clearances if you haven't recently. Above 200k is when they start to get near to out of spec. This may or may not be related to the misfire.

 

I agree with the compression test suggestion. This is a go - no go test. If the compression is decent and even across all cylinders then further diagnostics is required. If the compression is low but even across all cylinders then leak down test will show where the leakage is. If the leak down appears to be ok, check the valve clearances. In short, make sure she is mechanically sound before pursuing other things.

 

This problem ended up being my cylinder 1 injector. When I was driving and the miss started I pulled over and put the blade of a long screwdriver on the #2 injector and my ear on the handle. There was a very distinct ticking noise and on the #1 injector it was very muffled. I had replaced one once before but I don’t remember which one or what the symptoms were. Where I went wrong here is when I got the “misfire” code, because of the name I assumed it was ignition related but it seems that it applies to anything that results in the combustion stroke failing. I was surprised that there was not some type of code thrown that would’ve led me to check in the injectors. I’m guessing there probably is if there is a problem with the signal to the injector but there’s nothing to actually see that the injector does what it’s supposed to. Thanks for all the help here.

 

I am glad you found and repaired the misfire problem.